Resting Metabolic Rate Calculator Free

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Resting Metabolic Rate (RMR) Calculator

Calculate how many calories your body burns at rest.

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Understanding Your Resting Metabolic Rate (RMR)

Resting Metabolic Rate (RMR) represents the number of calories your body burns while at rest to maintain essential physiological functions such as breathing, circulation, and cell production. Even when you are not moving, your organs require energy to function correctly. Using a resting metabolic rate calculator free tool helps you establish a baseline for your daily caloric needs.

How the Calculation Works

This calculator utilizes the Mifflin-St Jeor Equation, which is widely considered the most accurate formula for predicting resting energy expenditure in healthy individuals. The formula accounts for your biological sex, weight, height, and age to provide a personalized estimate.

  • For Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
  • For Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161

RMR vs. BMR: What's the Difference?

While often used interchangeably, Basal Metabolic Rate (BMR) and Resting Metabolic Rate (RMR) have slight differences. BMR is measured under strict laboratory conditions after a 12-hour fast and 8 hours of sleep. RMR is a less restrictive measurement, typically taken after a period of rest, making it slightly higher than BMR but more practical for everyday use.

Why Your RMR Matters for Weight Loss

If your goal is weight management, knowing your RMR is the first step. To lose weight, you must create a "caloric deficit" by eating fewer calories than your Total Daily Energy Expenditure (TDEE). Your TDEE is your RMR plus the calories burned through physical activity and digestion. To gain weight or muscle, you would aim for a "caloric surplus."

Example: A 30-year-old male weighing 80kg and standing 180cm tall has an RMR of approximately 1,780 calories. If he leads a sedentary lifestyle, his total daily needs might be around 2,136 calories. Eating significantly below the RMR for extended periods can sometimes lead to metabolic adaptation, where the body slows down to conserve energy.

function calculateRMR() { var gender = document.getElementById("gender").value; var age = parseFloat(document.getElementById("age").value); var weight = parseFloat(document.getElementById("weight").value); var height = parseFloat(document.getElementById("height").value); var resultBox = document.getElementById("rmr-result-box"); var resultValue = document.getElementById("resultValue"); var resultText = document.getElementById("resultText"); if (!age || !weight || !height || age <= 0 || weight <= 0 || height <= 0) { alert("Please enter valid positive numbers for age, weight, and height."); return; } var rmr = 0; if (gender === "male") { // Mifflin-St Jeor for Men rmr = (10 * weight) + (6.25 * height) – (5 * age) + 5; } else { // Mifflin-St Jeor for Women rmr = (10 * weight) + (6.25 * height) – (5 * age) – 161; } var finalRmr = Math.round(rmr); resultValue.innerHTML = finalRmr + " kcal/day"; resultText.innerHTML = "This is the estimated amount of energy your body requires to maintain basic life functions while at rest."; resultBox.style.display = "block"; // Smooth scroll to result resultBox.scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }

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